Method of and apparatus for drying wet filament tows

ABSTRACT

Wet tows of filaments are dried on rotating drums at temperatures between 80* C. and 220* C. the surfaces of the drums having protuberances, for example in the form of wire fabric coverings, so that the vapors being formed between the two and the drum surface are able to escape through the interconnected cavities between the protuberances. Such drying of the tows imparts hardness to the handle of the fibers.

United States atent Gieseke, deceased et al.

METHOD OF AND APPARATUS FOR DRYING WET FILAIVENT TOWS Hans Alwin ErichGieseke, deceased, late of Dormagen, Germany by Ingrid Nora HansineGieseke, heir; Alfred Nogaj, Dormagen, Germany; Josef Schiefer, Cologne,Germany; Heinrich Rinkler, Dormagen, Germany Farbenfabriken BayerAktiengesellschaft, Leverkusen, Germany Filed: Aug. 13, 1970 Appl. No.:63,400

Inventors:

Assignee:

Foreign Application Priority Data Aug. 26, 1969 Germany .P 19 43 225.8

US. Cl ..34/9, 34/1 10 Int. Cl t t ..F26b 3/00 Field of Search ..34/l10,114,115, 122, 9

[451 May 30, 1972 Primary Examiner-John J. Camby Attorney-Burgess,Dinklage & Sprung [5 7] ABSTRACT Wet tows of filaments are dried onrotating drums at tempera tures between 80 C. and 220 C. the surfaces ofthe drums having protuberances, for example in the form of wire fabriccoverings, so that the vapors being formed between the two and the drumsurface are able to escape through the interconnected cavities betweenthe protuberances. Such drying of the tows imparts hardness to thehandle of the fibers 24 Claims, 3 Drawing Figures METHOD OF ANDAPPARATUS FOR DRYING WET FILAMENT TOWS This invention relates to amethod of and an apparatus for drying wet filament tows on rotatingdrums.

It is known that filament tows are conducted through driers of manydifferent constructional forms for drying purposes. The most usual ofthese are: screening drum driers, screening band driers and calenderdriers. These driers produce their drying action by the transmission ofthe heat energy of a heat carrier to the material to be dried and theconsequent evaporation therefrom of the adhering liquid. With thescreening drum and screening band driers, the heat carrier is generallyair, and with calender driers, the heat carrier is liquid or steam.Further transfer is effected either by blowing on to the tow or bydirect heat conduction. Another possibility of transferring heat energyis the radiation of a suitable heat radiator.

It is known that the properties of textile fibers can be substantiallyinfluenced at the time of their production by thermal treatments, forexample the capacity for shrinkage and elongation, the crimping, thedegree of whiteness or the handle of the fibers.

The handle of a textile material is expressed by the sensorialperception on gripping the material in the hand. It depends in acomplicated manner on the count, the bending modulus, the surfaceproperties and the friction of the separate fibers one against theother, on the yarn construction and also on the weight or thickness ofthe material. The handle is extremely important for judging a materialand for the feel thereof during wear. It is impossible to give ameasuring factor for the handle, because of the complex nature of thisproperty. It is graduated by the observer or by several observersaccording to terms such as soft, solid, hard, rough. A particularly softhandle is desirable for articles which are worn directly on the body,for example for under garments and socks. A full or solid handle isdesirable, for example, for carpet fibers.

When a tow is dried on a smooth, heated surface, a fiber material with asoft handle is obtained. On drying a textile web or a tow in an airstream, a fiber material with a solid handle is obtained.

The invention has for an object to adjust as desired the handle oftextile fibers and thus the handle of the yarns and manufacturedarticles produced therefrom by the drying method. At the same time, theoccluded vapors forming during the drying between smooth, heatedsurfaces and the tow are to be carried away.

This object is achieved according to the invention by the drum surfacesbeing heated and being maintained at a temperature between 80 C. and 200C., and by the heat transfer to the tow being effected by way ofprotuberances, so that the tow only comes into contact with theprotuberances.

The result hereby obtained is that vapors which are formed and collectbetween the drum surface and the tow can escape between theprotuberances. The drum surface is heated with steam, liquid orelectrically, without the heat carrier coming into direct contact withthe tow.

According to a further development of the method according to theinvention, a gaseous heat carrier additionally flows in a manner knownper se through the tow.

This combination of the method according to the invention with themethod as known per se permits a particularly good adaptation of thedrying procedure to different materials.

The tow is advantageously transported at a speed of from 30 to 100m/min.

The method according to the invention has proved to be especiallysuitable when used for drying tows consisting of polyacrylonitrilepolymers.

The apparatus of the invention for carrying the method into effectcomprises a rotatable drum with a closed wall or surface, which isprovided with a heating means. The feature according to the invention isthat the wall is provided with protuberances, between which continuousgaps extend.

The protuberances can have many different forms. According to oneembodiment of the invention, the protuberances consist of a fluting,produced, for example, by cutout grooves, which extend parallel to thedrum axis or crosswise relatively to one another. A strong roughening ofthe drum wall is also suitable.

A surface layer which has proved to be particularly simple tomanufacture and to be effective is one consisting of a wire fabric, wiregauze, a wire mesh or of a surface-structurized metal foil.

The required handle" can be adjusted for each material which is to bedried, according to the choice of the nature and density of theprotuberances. Thus, a punctiform or linear contact or even a small-areacontact of the drum wall with the towcan be produced, so that the directheat transfer is by way of the points of contact. With the interruptionsor gaps, there is a smaller heat transfer by radiation. In addition,however, the tow can also be irradiated by electric heat radiators.

According to one particular development of the invention, spacerelements are arranged between the covering layer and the drum wall, andducts or passages extend between these elements. The said ducts ensure alarger vapor space beneath the tow and thus a better extraction of thevapors which collect. The ducts are advantageously connected to asuction means. The use of a suction means has the advantage that thevapors removed by suction, and advantageously mixed with air, can beconveyed in a cycle, whereby special drying effects can be produced.However, in a manner known per se, it is only necessary for hot air orother treatment gases to be conveyed on to and drawn through the tow.

Connecting holes advantageously extend from the ducts through the drumwall into the interior of the latter, which is connected to a suctionmeans.

According to one particularly advantageous and constructionally simplefurther development of the invention, the heating means consist of boresextending in axial parallel relationship through the drum wall andthrough which a heating medium can flow.

Conventional drying drums can also be converted in a simple manner intothe apparatus according to the invention.

Three constructional examples of the apparatus according to theinvention are partly shown in strictly diagrammatic form in a drawing,wherein:

FIG. 1 shows a surface of a drum with a wire fabric cover- FIG. 2 showsa surface of a drum with a wire fabric covering and spacer elements; and

FIG. 3 is a showing of a calender dryer according to the invention.

In FIG. 1, a wall 1 of a steam-heated drum has a wire fabric covering 2fixed to the smooth surface thereof. For drying purposes, a tow 3 offilaments rests on this wire fabric 2. In this case, heat conduction,heat transfer and radiation are used for drying the material. The steamcondensed in the drum gives off its heat energy to the drum wall. Thistransmits the heat and transfers it to the wire fabric 2, which in itsturn transmits the heat and transfers it to the filament tow 3. At thesame time, the tow 3 receives the heat of radiation from the drum wall 1and the wire fabric 2 bearing thereon. Consequently, with contact, theheat is only transmitted by way of continuously interrupted surfaces.The steam forming between the tow 3 and drum wall 1 can discharge freelyinto the cavities of the wire fabric 2.

By the combination of smooth, uncovered drying drums and drying drumscovered with suitable wire fabrics 2, the required handle" isadjustable.

According to FIG. 2, a drum wall 21 is heated through bores 24 withsteam. The heat transfer is by way of a spacer element 25 to a slottedplate 26, on which is fixed a wire fabric 22. The filament tow 23 lieson the wire fabric 22. Passages 27, 28 extend between the spacerelements 25. The vapors and entrained air are discharged through bores29 and blown cyclically from above on to the tow 23 again. Consequently,in this example, the following physical inter-relationships are used forthe drying operation: transmission of the heat energy in gaseous form byhot gas being blown on to the tow, in liquid or vapor form by heatconduction and HEAT transfer, and also by radiation. The combination ofthese aforementioned types of heat transfer leads to the more intensiveand more rapid drying.

A calender heater or dryer, as is used in Example 2, for instance, isindicated in FIG. 3. The heater is composed of cooperating heated,rotatably mounted drums, including first drum 31 for receiving anarticle to be heated, intermediate drums 32, 33, 34, and 35, and a lastdrum 36 for discharge of the heated article. At least some of the drumsare of a construction as is shown in FIGS. 1 and 2. The first drum 31and the intermediate drums adjacent thereto, 32 and 33, are ofconstruction as is shown in FIGS. 1 and 2, having protuberances 37 attheir outer surfaces. The last drum and the intermediate drums adjacentthereto have smooth outer surfaces 38.

EXAMPLE 1 A tow of polyacrylonitrile filaments is stretched by 260percent in water at 98 C. After the stretching, the tow has a totalcount of 270,000 dtex. The count of the individual filament is 3.3 dtex.The tow is washed in water at 80 C. and provided with a finishingpreparation. The tow is thereafter dried in conventional manner at aspeed of 50 m/min. on a calender drier with 28 calender drums at atemperature of 130 C. The tow which is produced is crimped in the usualmanner and cut into staple fibers. The fibers are processed into yarnsand dyed. The dyed yarns are tested for their handle. The materialproduced by the conventional drying method provides a yarn with a softhandle.

EXAMPLE 2 A wet filaments tow pretreated in the same manner as inExample l is dried on a calender drier, the 28 drums of which areprovided in accordance with the invention with a screening wire fabric.The wire fabric consists of a chrome-nickel steel. The thickness of thewire is 0.18 mm and the number of meshes is 450 meshes per squarecentimeter. After drying, further processing takes place as inExample 1. The material dried and produced in this way provides a yarnwith a compact or solid hand1e".

EXAMPLE 3 A tow of polyacrylonitrile filaments is stretched by 260percent in water at 98 C. After the stretching, the tow has a totalcount of 270,000 dtex, the count of the individual filament being 3.3dtex. The tow is washed in water at 80 C. and provided with a finishingpreparation. The tow is thereafter dried at a speed of 50 m/min. on acalender drier having 28 calender drums. The first l2 drums are providedwith a screening wire fabric, as in Example 1, and the last 16 drums aresmooth. The first l2 drums are heated to 140 C. and the last 16 drums to100 C. The tow is worked up in the usual manner into staple fibers. Theyarn produced therefrom has a softer handle than the yarn preparedaccording to Example 2 and a fuller or more solid handle than the yarnproduced according to Example 1.

EXAMPLE 4 A tow of polyacrylonitrile filaments is stretched by 360percent in water at 98 C. After the stretching, the tow has a totalcount of 180,000 dtex, the count of the separate filament being 3.3dtex. The tow is washed in water at 80 C. and provided with a finishingpreparation. The tow is thereafter conveyed at a speed of 60 m/min. intoa calender drier with 28 calender drums. The peripheral speed of thefirst 8 drums is 60 m/min., that of the 9th to 12th drums is 54 m/min.and that of the 13th to 28th drums is 51 m/min. The temperature of thedrums l to 4 is 80 C., that of drums to 8 is 140 C. and that of drums 9to 28 is 130 C. The tow is thereafter crimped and laid as an endlessband.

EXAMPLE 5 In another experiment, a tow is conveyed as in Example 4 intoa calender drier, of which the smooth drums are provided with ascreening wire fabric, as in Example 2. The speed setting of thecalender drums is as Example 4, but the temperatures are in each caseset 20 C. higher. The dried tow is crimped and laid as an endless band.

The endless bands produced according to Example 4 and 5 are processed ona turbo-stacker and processed in the usual way to form bulk yams. Theyarns are dyed and finished and tested for their handle. The yarnproduced according to Example 4 has a soft handle, while the yarnproduced according to Example 5 has a solid handle.

We claim:

1. Process for drying wet tows and controlling the handle of the fibersof the dry tow which comprises:

a. operating a conduction heater for supplying of heat thereby, saidheater having a heat transferring surface defined by protuberancesproviding outwardly disposed areas for heat transfer by conduction fromthe heater, and cavities between the protuberances,

. contacting a flat surface of the tow with said heat transferringsurface for heating of the tow and at least partial drying thereof,

c. said operating of the conduction heater comprising the heatingthereof for transfer of heat by conduction from the conduction heaterheat transferring surface to the tow.

2. Process according to claim 1, said heat transferring surface beingporous for escape of vapors.

3. Process according to claim 2, wherein a gas is passed through the towto improve the drying.

4. Process according to claim 1, said conduction heater being a drumdryer in which the outwardly disposed surface of the drum forms saidheat transferring surface, and transporting the tow over the surface ofthe dryer during the drying.

5. Process according to claim 4, the tow being transported at a speed of30 to 100 m/min.

6. Process according to claim 1, the temperature of said heattransferring surface being between C. and 200 C.

7. Process according to claim 1, the tow being composed ofpolyacrylonitrile fibers.

8. Process according to claim 1, the tow being composed ofpolyacrylonitrile fibers, the temperature of said heat transferringsurface being 80 C. to 200 C, said conduction heater being a drum dryerin which the outwardly disposed surface of the drum forms said heattransferring surface, and transporting the tow over the surface of thedryer during the drying, at a speed of 30 to m/min.

9. Process of producing fibrous yarn of a desired handle from a wet towof the fibers which comprises drying the tow by the process of claim 1,and producing the yarn from the dried IOW.

10. Process according to claim 12, and utilizing a heat carrier for saidheating the heat carrier supplying heat for the conduction heatingwithout the heat carrier coming into direct contact with the tow.

11. A conduction heater suitable for drying wet lows comprising:

a. rotatable drum having a cylindrical outer wall,

b. protuberances disposed on the outer surface of said wall producingoutwardly disposed areas for heat transfer by conduction from theheater, and cavities between the protruberances,

c. means for heating by a heat carrier means said wall for transfer ofheat thereby to said protuberances for transfer of heat to the wall anddirectly from the wall to a tow placed in contact with the wall, withoutthe heat carrier means coming into direct contact with the tow.

12. Heater according to claim 1 1, said cavities intercommunicating anddefining continuous gaps.

13. Heater according to claim 12, said protuberances being defined byfluting.

14. Heater according to claim 12, said protuberances being formed byporous wire sheet.

Heater according to claim 12, said protuberances being formed bysurface-structurized metal foil 16. Heater according to claim 11, andmeans defining passageways in said wall communicating with the cavitiesfor removal of gas from the cavities during heating of an article by theheater.

17. Heater according to claim 16, and suction means for drawing gas fromthe cavities through said passageways during heating.

18. Heater according to claim 11, said protuberances being formed by aporous wire sheet overlying said wall, a porous spacer elementinterposed between said wire sheet and said wall supporting the wiresheet, and means defining ducts in said wall for passage of gas throughthe wire sheet spacer elements, and ducts.

19. Heater according to claim 18, and suction means for drawing gasthrough said ducts.

20. Heater according to claim 18, and passageways communicating saidducts with the interior of the drum, and suction means for withdrawinggas from the interior of the drum.

21. Calender heater composed of cooperating rotatable heated drumsincluding a first drum for receiving an article to be heated and a lastdrum for discharge of the heated article, at least some of the drums areaccording to claim 1 l.

22. Calender heater composed of cooperating rotatable heated drumsincluding a first drum for receiving an article to be heated and a lastdrum for discharge of the heated article, all of the drums beingaccording to claim 1 l.

23. Calender heater composed of cooperating rotatable heated drumsincluding a first drum for receiving an article to be heated and a lastdrum for discharge of the heated article, part of the drums beingaccording to claim 11, and part of the drums having a smooth outersurface for transfer of heat from the drum to the article.

24. Calender heater composed of cooperating rotatable heated drumsincluding a first drum for receiving an article to be heated and a lastdrum for discharge of the heated article, and several drums intermediatesaid first drum and said last drum, the first drum and intermediatedrums adjacent thereto being according to claim 11, the last drum andintermediate drums adjacent thereto having a smooth outer surface fortransfer of heat from the drum to the article.

1. Process for drying wet tows and controlling the handle of the fibersof the dry tow which comprises: a. operating a conduction heater forsupplying of heat thereby, said heater having a heat transferringsurface defined by protuberances providing outwardly disposed areas forheat transfer by conduction from the heater, and cavities between theprotuberances, b. contacting a flat surface of the tow with said heattransferring surface for heating of the tow and at least partial dryingthereof, c. said operating of the conduction heater comprising theheating thereof for transfer of heat by conduction from the conductionheater heat transferring surface to the tow.
 2. Process according toclaim 1, said heat transferring surface being porous for escape ofvapors.
 3. Process according to claim 2, wherein a gas is passed throughthe tow to improve the drying.
 4. Process according to claim 1, saidconduction heater being a drum dryer in which the outwardly disposedsurface of the drum forms said heat transferring surface, andtransporting the tow over the surface of the dryer during the drying. 5.Process according to claim 4, the tow being transported at a speed of 30to 100 m/min.
 6. Process according to claim 1, the temperature of saidheat transferring surface being between 80* C. and 200* C.
 7. Processaccording to claim 1, the tow being composed of polyacrylonitrilefibers.
 8. Process according to claim 1, the tow being composed ofpolyacrylonitrile fibers, the temperature of said heat transferringsurface being 80* C. to 200* C, said conduction heater being a drumdryer in which the outwardly disposed surface of the drum forms saidheat transferring surface, and transporting the tow over the surface ofthe dryer during the drying, at a speed of 30 to 100 m/min.
 9. Processof producing fibrous yarn of a desired handle from a wet tow of thefibers which comprises drying the tow by the process of claim 1, andproducing the yarn from the dried tow.
 10. Process according to claim12, and utilizing a heat carrier for said heating the heat carriersupplying heat for the conduction heating without the heat carriercoming into direct contact with the tow.
 11. A conduction heatersuitable for drying wet lows comprising: a. rotatable drum having acylindrical outer wall, b. protuberances disposed on the outer surfaceof said wall producing outwardly disposed areas for heat transfer byconduction from the heater, and cavities between the protruberances, c.means for heating by a heat carrier means said wall for transfer of heatthereby to said protuberances for transfer of heat to the wall anddirectly from the wall to a tow placed in contact with the wall, withoutthe heat carrier means coming into direct contact with the tow. 12.Heater according to claim 11, said cavities intercommunicating anddefining continuous gaps.
 13. Heater according to claim 12, saidprotuberances being defined by fluting.
 14. Heater according to claim12, said protuberances being formed by porous wire sheet.
 15. Heateraccording to claim 12, said protuberances being formed bysurface-structurized metal foil
 16. Heater according to claim 11, andmeans defining passageways in said wall communicating with the cavitiesfor removal of gas from the cavities during heating of an article by theheater.
 17. Heater according to claim 16, and suction means for drawinggas from the cavities through said passageways during heating. 18.Heater according to claim 11, said protuberances being formed by aporous wire sheet overlying said wall, a porous spacer elementinterposed between said wire sheet and said wall supporting the wiresheet, and means defining ducts in said wall for passage of gas throughthe wire sheet spacer elements, and ducts.
 19. Heater according to claim18, and suction means for drawing gas through said ducts.
 20. Heateraccording to claim 18, and passageways communicating said ducts with theinterior of the drum, and suction means for withdrawing gas from theinterior of the drum.
 21. Calender heater composed of cooperatingrotatable heated drums including a first drum for receiving an articleto be heated and a last drum for discharge of the heated article, atleast some of the drums are according to claim
 11. 22. Calender heatercomposed of cooperating rotatable heated drums including a first drumfor receiving an article to be heated and a last drum for discharge ofthe heated article, all of the drums being according to claim
 11. 23.Calender heater composed of cooperating rotatable heated drums includinga first drum for receiving an article to be heated and a last drum fordischarge of the heated article, part of the drums being according toclaim 11, and part of the drums having a smooth outer surface fortransfer of heat from the drum to the article.
 24. Calender heatercomposed of cooperating rotatable heated drums including a first drumfor receiving an article to be heated and a last drum for discharge ofthe heated article, and several drums intermediate said first drum andsaid last drum, the first drum and intermediate drums adjacent theretobeing according to claim 11, the last drum and intermediate drumsadjacent thereto having a smooth outer surface for transfer of heat fromthe drum to the article.